Mechanism of FASCICLIN LIKE ARABINOGALACTAN PROTEIN 4

Each plant cell is surrounded by a cell wall. The unique construction and dynamics of plant cell walls enable rapid growth while maintaining strength, forming the structural basis of the plant world that surrounds and nourishes us. To maintain the function of the cell wall during growth, especially in times of environmental changes, plants possess a complex control system that checks the structure and function of cell wall molecules and adjusts them according to the varying conditions. Although several components of this cell wall control system have been discovered in recent years, there is still much to be learned. For example, the family of Fasciclin Arabinogalactan (FLA) proteins plays an important role in this control system, but how FLA proteins function at the molecular level remains completely unknown. The present project aims to fill this knowledge gap. As a representative of the FLA family, we are investigating the function of FLA4, a protein necessary for normal cell elongation and cell wall structure in plants. Studies on mutants of the model plant Arabidopsis thaliana have shown that the function of FLA4 depends on two receptor proteins, FEI1 and FEI2, and it has been speculated that FLA4 and the FEI proteins form a complex. However, other molecules, including proteins and cell wall polymers, could also bind to FLA4 and thereby modify its activity. These hypotheses will be experimentally tested here. We aim to investigate whether FLA4 and the FEIs interact in the cell and whether other proteins also bind to FLA4. We will also examine whether FLA4 binds to complex polymers of the cell wall. Can FLA4 diffuse from one cell through the cell wall and act in neighboring cells? Can FLA4 change its shape and thus transmit information about the current structure of the cell wall to receptor proteins? Answers to these questions would expand our understanding of the mechanisms of plant growth and provide clearer insight into the regulation of cell wall structure. Since the plant cell wall is one of the most important renewable resources, insights from this fundamental project could contribute to the development of technologies for improved production of cell wall-based raw materials or more adaptable crops.